add vboxsf group (for automatic mounting of shared folders)
xserver: Allow to add extra options to xorg config.

This is especially useful if you want to supply a default XRandR configuration,
where you need multiple "Monitor" sections in order to set properties for
specific CRTCs (if not running in zaphod mode).

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
xserver: Allow to set XRandR multi head layout.

This is currently only a very simple implementation which just recurses a list
of heads that get chained together to the right of the corresponding previous
item of the list.

If I forgot about something in the already existing configuration options,
please let me know or if this commit is useless or a duplicate, feel free to
revert. But by looking at implementation before this commit, I only see zaphod
and/or quirky xinerama-like configuration options.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Revert "xserver: Allow to add extra options ...

This reverts commit 1e741f1572b6793b861e2f9820015475ce339ae0 as it is
unnecessary according to @edolstra, because services.xserver.config from another
module will be merged into the configuration.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Merge pull request #60 from dysinger/virtualbox-guest-additions-vboxsf-group

VirtualBox Guest Additions: add vboxsf group (for automatic mounting of shared folders)